This lesson helps introduce students to the concept that temperature causes molecules and atoms to move faster and farther apart, which in turn causes the change from solid to liquid, and liquid to gas.

Mercury Sunrise

Above the Arctic Circle, half the year is spent in darkness while the other half is spent in almost continuous sunlight. Some researchers have found that that seasonal cycle might be contributing to environmental pollution of the area. You'll hear why in this Science Update.

Transcript

Pollution from an Arctic sunrise. I'm Bob Hirshon and this is Science Update.

Few places remain as untouched as the beautiful Arctic wilderness. But Steve Lindberg, a researcher at Oak Ridge National Lab, says a dangerous pollutant has turned up in this once pristine place.

Lindberg: A number of studies have shown highly elevated concentrations of mercury in various Arctic biota—in birds, and in mammals and in fish.

Now, Lindberg and his colleagues have learned why the Arctic is getting more than its share of mercury. He says mercury gas is blown into the atmosphere from factories, volcanoes, and landfills. It travels around the globe, some of it accumulating in the air over the Arctic during the long, dark winter. Then once spring arrives, that mercury rains down.

Lindberg: A series of unusual chemical reactions can occur as a result of it having been dark for many months, such that when the sun first comes up, it begins to react with things that have accumulated in the atmosphere while it was dark.

Lindberg says the phenomenon, dubbed Mercury Sunrise, releases twice as much mercury in four months than other regions get in a whole year. He says researchers are now investigating just how harmful this phenomenon is to the environment. For the American Association for the Advancement of Science, I'm Bob Hirshon.

Making Sense of the Research

Mercury is a powerful neurotoxin (a poison that affects nerve and brain function). It can cause strange behavior, a loss in motor functions (for example, numbness in the fingers), birth defects, and death. So it's not something you want lying around in the environment.

Unfortunately, mercury travels very efficiently. According to Lindberg, if you broke a thermometer in your backyard (do NOT try this at home!), the mercury that escaped into the air would disperse across the whole planet in less than a week. When you consider that fossil fuel-burning factories all over the world are pumping mercury into the air on a regular basis, it's not hard to see how it could spread to an isolated place like the Arctic.

However, what caught scientists' attention was not that mercury was showing up in the Arctic wildlife at all, but that it was showing up in greater and greater quantities even though the amount of mercury being emitted by factories is going down. That's what led to the discovery of the "Mercury Sunrise" phenomenon.

The key to Mercury Sunrise is the rate at which inert mercury gas in the air is oxidized. The oxidized mercury gas is known as "sticky gas" because it binds easily with the surfaces of other molecules. Mercury is oxidized naturally in all parts of the world, but during the Arctic sunrise, the process takes minutes to hours instead of months or years. As a result, the concentration of "sticky" mercury in the snow rises rapidly during the Arctic spring. When the snow melts, the mercury is flushed into the ocean and groundwater, and works its way into fish, birds, and the animals that eat them.

One would hope that the decrease in global mercury emissions would make the Arctic situation improve. However, Lindberg notes that ultraviolet light, open water, and active sea ice (ice that melts and re-freezes) are all increasing in the Arctic, thanks to global warming and the hole in the ozone layer. And all of these factors seem to enhance the Mercury Sunrise effect. So we may not see an improvement for many years to come.

Now try and answer these questions:

How do mercury emissions from the United States, Russia, or China affect the Arctic?

Why are the mercury levels so high in the Arctic?

Think about the mercury that runs off into the Arctic Ocean from contaminated snow. How might people or animals in your local area eventually be affected by this?

Can you think of other kinds of pollution or human activities that affect distant environments?